Patent GB-1107586-A (GB)
Title: Unidirectional-signal circuit arrangements with d.c. isolation
IPC: G01R27/12
Filed: 1965-07-20
Abstract: 1,107,586. Multiplying and dividing circuits. SIEMENS A.G. 20 July, 1965 [7 Aug., 1964], No. 30891/65. Heading G4G. [Also in Divisions G1 and H3] In an amplifying circuit wherein an input circuit operates upon an output circuit but is isolated therefrom for direct current, the input voltage energizes an inductance whose core field controls the resistance of a magneto-resistive semi-conductor in an arm of a bridge whose output diagonal is connected to the output circuit and whose input diagonal is fed with a constant voltage or one representing a variable to be multiplied by that represented by the input voltage, the core being premagnetized for linearity, and further magnetized by a winding in the bridge output circuit (Fig. 1, not shown). In a modification (Fig. 2), voltage U 1  energizes winding L 1  of core K 1  premagnetized for linearity by winding L 1 <SP>1</SP> energized from D.C. source Q, and the core field controls the resistance of magneto-resistive element F 1  in an airgap thereof, which is connected with resistances R 1 <SP>1</SP>, R 1 <SP>11</SP>, R 1 <SP>111</SP> in bridge W 1  to whose diagonal AB is applied voltage U 2 . The output diagonal CD energizes winding L 2  of core K 2  in an airgap of which is magneto-resistive element F 2 ; connected in a further bridge W 2  with resistances R 2 1, R 2 <SP>11</SP>, R 3 <SP>11</SP> energized from D.C. source Q<SP>1</SP> to develop at its output diagonal voltage U a  proportional to U 1 U 2 . Core K 2  is premagnetized for linearity by winding L 2 <SP>1</SP> energized from D.C. source Q 2 . In a further modification (Fig. 5, not shown) the linear operating range is increased and the effect of temperature changes reduced by connecting the input voltage U over opposed polarity half-wave rectifiers to windings of separate cores having separate premagnetization windings; the field of each core controlling the resistance of its own magnetoresistive element, connected in adjacent arms of a bridge energized by the input voltage U 2  ; the output diagonal of the bridge energizing windings of separate cores with separate premagnetizing windings controlling other magneto-resistive elements connected with resistance elements in a bridge energized from a constant voltage source to produce an output voltage representing the product of the input voltages. In a further modification (Fig. 6, not shown), the core energized by the input voltage U 1  controls a magneto-resistive element in a constant energization bridge whose output excites a negative feedback winding on the core and controls a further magneto-resistive element in a bridge energized by the input voltage U 2 ; the output of this bridge energizing other cores controlling corresponding magnetoresistive elements which are connected in adjacent arms of a constant energization bridge whose output voltage represents U 1 U 2  and energizes feedback windings of the respective cores. In a further modification (Fig. 7, not shown) the input voltage U 1  energizes a first core to control a magneto-resistive element connected in a bridge whose output is amplified by the circuit of Fig. 1 (not shown) to produce an output voltage U A  and to energize a feedback winding of the core. The bridge is energized by input voltage U 2  in series with a winding of a second core controlling two magneto-resistive elements; one of which is connected in a bridge whose output energizes a feedback winding of the second core, and the other which is connected in series with the feedback winding of the first core. U A  = U 1 U 2 . The circuit is also applicable to division.